1. Field of the Invention
The present invention relates to an optical unit for a probe, and optical unit producing method. More particularly, the present invention relates to an optical unit for a probe, and optical unit producing method, in which the probe of a probe apparatus is used for in-vivo imaging of a tissue in a human cavity of a patient's body, and an image of the tissue can be stably obtained owing to an improved assembly of the optical unit.
2. Description Related to the Prior Art
A confocal laser probe of a probe apparatus is known, including an optical unit disposed at a distal end of single-mode optical fibers. The optical unit applies laser light to a tissue of a gastrointestinal tract in a patient Is body. Among components of the laser light reflected by the tissue, only reflected light at the focal plane of the optical unit on an object side, an object image of the tissue is obtained. U.S. Pat. Pub. No. 2004/156124 (corresponding to JP-A 2004-240346) discloses an example of the confocal laser probe. According to optical tomography, a two-dimensional image can be obtained at a depth of approximately 100 microns under the surface of mucous membranes by scanning the tissue with the laser light.
JP-A 2000-121961 discloses the use of the confocal laser probe by insertion in a forceps channel of an electronic endoscope. The confocal laser probe must have a small outer diameter for the purpose of reducing physical load to a patient Is body. Also, it is necessary for the optical unit to have a high numerical aperture NA, because a focal plane of the optical unit should be set for a position with a depth from a surface of the tissue. A high value of the numerical aperture NA is essentially necessary specifically with a great wavelength of the laser light in order to create images of high definition.
Lens optics constituting the optical unit must have very fine sizes owing to technical progress according to small diameters and high value of the numerical aperture NA. It has been very difficult to position the lens optics with one another at very high precision. U.S. Pat. No. 7,471,472 (corresponding to JP-A 2007-208533) discloses a method of assembling the lens optics by use of a specialized tool in order to determine intervals between the lens optics precisely.
Owing to requirement of fine sizes of the lens optics in the optical unit, a distance between the focal plane and a first lens/lens group opposed to the tissue is made as small as 50 microns. It is necessary for the first lens/lens group to contact the tissue. An image in the tissue cannot be created with high quality if the contact between the first lens/lens group and the tissue is insufficient.
A portion of the first lens/lens group at the distal end of the lens barrel is coated with adhesive agent for reinforcement. However, various problems arise with the structure of the end of the first lens/lens group flush with the distal end of the lens barrel, for example, difficulty in applying a coating, insufficiency in the reinforcement, addition of a step of wiping the adhesive agent to remove dirt of the first lens/lens group, and the like.